The present invention relates to a pin header designed to be surface mounted on a printed circuit board, and more particularly to a pin header comprising a plurality of pin contacts that are arranged in parallel upper and lower rows and through an insulating housing. The invention further relates to a method of making this type of pin header, wherein the housing is of a rectangular parallelepiped shape and insert-molded using the pin contacts that serve as inserts to be embedded in the molded housing.
FIGS. 8 and 9 show an example of the prior art pin header 1. This pin header has a plurality of pin contacts 2 that form upper and lower rows in an insulating housing 3. The housing is generally of a parallelepiped shape and insert-molded with the plurality of pin contacts 2 each penetrating it. Each pin contact 2 is composed of a plugging rod 4 extending horizontally, a leg 5A or 5B and a generally straight and horizontal extension 6, all integral with each other. The plugging rod 4 protruding from a front face 3a of the housing 3 has a rear end that is exposed on a rear face of this housing. The rear end is bent downwards generally at a right angle to provide the leg 5A or 5B. Each leg has its lower end continuing at a right angle to the horizontal and straight extension 6 that is to be surface-mounted on a printed circuit board xe2x80x98Pxe2x80x99. Those legs 5A, which the pin contacts 2A forming the upper row near the upper face of the housing 3 do have, are much longer than the other legs 5B which the other contacts 2B forming the lower row have. As will be seen in FIGS. 10 and 11, formed in the rear end of each plugging rod 4 is such a shoulder 7 as thinning a rearward region of each contact 2A and 2B. Thus, each leg 5A and 5B as well as each rear straight extension 6 are made thinner than the body of each plugging rod. A crosspiece 8 formed integral with rearward ends of the extensions 6 holds the upper or lower contacts 2A and 2B at a regular pitch while insert molding them in the housing 3, until being subsequently cut off to provide a finished product.
The insert molding of the housing 3 with upper and lower contacts 2A and 2B will be carried out as shown in FIG. 12, wherein each upper contact 2A with a longer leg 5A is retained at three pints. In detail, a mold segment xe2x80x98Kxe2x80x99 holds therein the contact""s plugging rod 4, whilst other segments xe2x80x98Lxe2x80x99 and xe2x80x98Mxe2x80x99 grip the rod""s rear end 4xe2x80x2, with the segment xe2x80x98Lxe2x80x99 and another segment xe2x80x98Nxe2x80x99 griping the crosspiece 8. Due to a considerably long distance from the rear ends 4xe2x80x2 to the common crosspiece, the upper contacts have been likely to make unintentional movement within the mold. Consequent distortion of the housing 3 in position as a whole has adversely affected xe2x80x98coplanarityxe2x80x99 of the straight extensions 6 affixed to the circuit board. If thickness xe2x80x98Sxe2x80x99 of the housing 3 were reduced in a fore and aft direction to provide a thinnest possible pin header 1, then this problem would be more serious. Such a reduced thickness xe2x80x98Sxe2x80x99 has caused another problem that the housing 3 could not surely hold the pin contacts 2, failing to protect their shoulders 7 from breakage against torsion or a bending stress imparted to the rods 4 when plugging them in sockets.
An object of the present invention made in view of such drawbacks is therefore to provide an improved pin header and a method of making same, wherein contacts forming an upper row do scarcely make any unintentional movement while being insert molded and the resultant pin header is protected in its entirety from positional distortion. Another object is to provide a pin header that does not only ensure xe2x80x98coplanarityxe2x80x99 of its rear, horizontal and straight extensions but also have plugging rods resistant to torsion or a bending stress, so that the pin header can be made thinner in dimension.
To achieve these objects, a pin header provided herein has a plurality of pin contacts forming upper and lower rows in an insulating housing. The housing is generally of a parallelepiped shape and insert-molded with the pin contacts each penetrating it. Each pin contact is composed of a plugging rod extending horizontally, a leg and a generally straight and horizontal extension, all integral with each other. The plugging rod protruding from a front face of the housing has a rear end that is exposed on a rear face of this housing, with the rear end being bent downwards generally at a right angle to provide the leg. Each leg has its lower end continuing at a right angle either directly or indirectly to the rearward, horizontal and straight extension that is to be surface-mounted on a printed circuit board. Characteristically, only those legs of the pin contacts forming the upper row in the housing have each an intermediate step (19) at a corner between the leg and the horizontal extension. The intermediate step is formed by twice-bending each leg outwardly at first at a right angle and then downwards also at a right angle. Thus, the legs of the pin contacts forming the upper row are embedded in the housing, with the intermediate step of each contact being exposed outside together with the rearward horizontal extension.
Preferably, a shoulder may be formed in a middle region of the leg so as to render each leg and each rear straight extension thinner than the body of each plugging rod.
A method provided herein for manufacturing the pin header just summarized does comprise the step of preparing pin contacts whose rear horizontal and straight extensions to be surface-mounted on a printed circuit board are arranged at a predetermined pitch and in parallel with each other and are integrally connected to a common crosspiece. The method further comprises the steps of setting the pin contacts in an injection mold so as to form therein an upper row and a lower row, and finally insert-molding an insulating housing so that plugging rods of the contacts continue from respective legs and protrude forwardly of the housing, with the rear extensions continuing from the legs and protruding rearwardly of said housing. Characteristic to this method are the following features that the contacts forming the upper row in the housing do have each an intermediate step (19) at a corner between the leg and the horizontal extension, where in the intermediate step is formed by twice-bending each leg outwardly at first at a right angle and then downwards also at a right angle, and that during the step of insert molding the housing each contact forming the upper row is kept supported at four points in and by the mold, that is, at its plugging rod, at its rear surface area of the leg, at its intermediate step and at the crosspiece. Therefore, the entirety of each leg except for its rear surface area supported on a portion of the mold is embedded in the insulating housing thus molded.